Ink-jet inks typically comprise an ink vehicle and a colorant, the latter of which may be a dye or a pigment. Dye-based ink-jet inks used in photographic image printing are almost always water-soluble dyes. As a result, such dye-based ink-jet inks are usually not very water fast, i.e. images tend to shift in hue and edge sharpness is reduced upon exposure to humid conditions. In addition, images created from these water-soluble dye-based ink-jet inks tend to fade over time, such as when exposed to ambient light and/or air. Pigment-based inks on the other hand, allow the creation of images that are vastly improved in humid fastness and image fade resistance. Pigment based images, however, are inferior to dye-based ink-jet inks with respect to the desirable trait of color saturation.
Print media surfaces play a key role in the fade properties and humid fastness of ink jet produced printed images. Thus, for a given ink, the degree of fade and humid fastness can be dependent on the chemistry of the media surface. This is especially true in the case of dye-based ink jet ink produced images. As a result, many ink-jet inks can be made to perform better when an appropriate media surface is used.
In order for the ink jet industry to effectively compete with silver halide photography, it is desirable that ink jet produced images be color saturated, fade resistant, and humid fast, to name a few goals. Thus, enhanced permanence of dye-based ink-jet ink produced images is becoming more and more integral to the long-term success of photo-quality ink-jet ink technologies.
A few categories of photographic ink-jet media are currently available, including polymer coated media, clay coated media, and porous coated media. It is the polymer-coated media that provides for the longest lasting ink-jet ink produced images. However, this category of media is generally inferior in dry time and humid fastness relative to porous coated media. On the other hand, image fade resistance and humid fastness of porous coated media is generally lower than that of its polymer coated media counterpart. Therefore, there is a great desire to improve the image permanence of ink jet ink images printed on porous coated media.
Image permanence improvements have been attempted via modification of the ink. They have also been attempted via modification of the media. Surface modification of porous media coatings is one of the methods of media modification that has been attempted. Such modifications have been carried out in organic solvents, which can be costly and complicated at scale up, as well as pose environmental concerns. Simpler and more economical modification methods giving a desired end result would be an advancement in the art.